Wireless Power Supply System and Power Transmission Device

ABSTRACT

A wireless power supply system includes a power transmission device having a power transmission coil and a power receiving device having a power receiving coil. The power transmission coil transmits electric power to the power receiving coil via a wireless connection. The power transmission device includes a power factor calculator configured to calculate a power factor based on a phase difference between a voltage and a current supplied to the power transmission coil, and a control amount calculator configured to control electric power supplied to the power transmission coil according to a power command value, and regulate the electric power supplied to the power transmission coil when the power factor falls to a predetermined threshold power factor or less. The power transmission can therefore be regulated immediately when the power receiving coil is shifted from the power transmission coil.

TECHNICAL FIELD

The present invention relates to a wireless power supply system and apower transmission device for supplying electric power via a wirelessconnection to a vehicle, such as an electric vehicle equipped with abattery.

BACKGROUND

Wireless power supply systems have been proposed that supply electricpower to electrical loads mounted on vehicles via a wireless connectionbetween power transmission devices provided on the ground side and powerreceiving devices provided on the vehicle side. A vehicle using such awireless power supply system and parked in a power supply position maybe moved from the power supply position during power supply. The systemis required to immediately detect a positional shift between a powertransmission coil and a power receiving coil due to the movement of thevehicle so as to stop the power supply.

For example, International Publication WO 2013/046391 discloses a systemin which a power transmission device and a power receiving devicecommunicate with each other so as to control an appropriate supply ofvoltage. International Publication WO 2013/046391 discloses that thecommunication between the power transmission device and the powerreceiving device is implemented for a second cycle, and the powertransmission device is controlled so as to appropriately transmitelectric power for a first cycle shorter than the second cycle.

International Publication WO 2013/046391 fails to disclose that thepower transmission is regulated when the positions of the powertransmission coil and the power receiving coil are shifted from eachother during wireless power supply.

SUMMARY

The present invention has been made in view of the conventional problemdescribed above. An object of the present invention is to provide awireless power supply system and a power transmission device capable ofregulating power transmission when positions of a power transmissioncoil and a power receiving coil are shifted from each other.

A wireless power supply system according to an aspect of the presentinvention includes a power transmission device having a powertransmission coil and a power receiving device having a power receivingcoil, and the power transmission coil transmits electric power to thepower receiving coil via a wireless connection, so as to supply theelectric power to an electrical load installed in the power receivingdevice. The power transmission device includes a power factor calculatorconfigured to calculate a power factor based on a phase differencebetween a voltage and a current supplied to the power transmission coil,and a power controller configured to control electric power supplied tothe power transmission coil according to a transmission power commandvalue, and regulate the electric power supplied to the powertransmission coil when the power factor falls to a predeterminedthreshold power factor or less.

A power transmission device according to an aspect of the presentinvention has a power transmission coil and supplies electric power viaa wireless connection to an electrical load installed in a powerreceiving device having a power receiving coil. The power transmissiondevice includes a power factor calculator configured to calculate apower factor based on a phase difference between a voltage and a currentsupplied to the power transmission coil, and a power controllerconfigured to regulate electric power supplied to the power transmissioncoil when the power factor falls to a predetermined threshold powerfactor or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a wireless powersupply system according to an embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration of a wireless powersupply system according to a first embodiment of the present invention;

FIG. 3 is a flowchart showing a processing procedure of a powertransmission controller in the wireless power supply system according tothe first embodiment of the present invention;

FIG. 4 is a flowchart showing a processing procedure of a powerreceiving controller in the wireless power supply system according tothe first embodiment of the present invention;

FIG. 5 is a block diagram showing a control amount calculator in thewireless power supply system according to the first embodiment of thepresent invention;

FIG. 6 is a block diagram showing a configuration of a wireless powersupply system according to a second embodiment of the present invention;

FIG. 7 is a flowchart showing a processing procedure of a powertransmission controller in the wireless power supply system according tothe second embodiment of the present invention;

FIG. 8 is a flowchart showing a processing procedure of a powerreceiving controller in the wireless power supply system according tothe second embodiment of the present invention;

FIG. 9 is a block diagram showing a configuration of a wireless powersupply system according to a third embodiment of the present invention;

FIG. 10 is a flowchart showing a processing procedure of a powertransmission controller in the wireless power supply system according tothe third embodiment of the present invention;

FIG. 11 is a flowchart showing a processing procedure of a powerreceiving controller in the wireless power supply system according tothe third embodiment of the present invention;

FIG. 12 is a block diagram showing a configuration of a wireless powersupply system according to a fourth embodiment of the present invention;

FIG. 13 is a flowchart showing a processing procedure of a powertransmission controller in the wireless power supply system according tothe fourth embodiment of the present invention;

FIG. 14 is a flowchart showing a processing procedure of a powerreceiving controller in the wireless power supply system according tothe fourth embodiment of the present invention;

FIG. 15 is a block diagram showing a configuration of a wireless powersupply system according to a modified example of the fourth embodimentof the present invention;

FIG. 16 is a flowchart showing a processing procedure of a powertransmission controller in the wireless power supply system according tothe modified example of the fourth embodiment of the present invention’and

FIG. 17 is a flowchart showing a processing procedure of a powerreceiving controller in the wireless power supply system according tothe modified example of the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the drawings. FIG. 1 is a block diagram showing aconfiguration of a wireless power supply system according to the presentinvention. As shown in FIG. 1, a vehicle 200 includes a power receivingdevice 40. A power transmission device 10 for supplying electric powerto the vehicle 200 is provided on the ground side in a parking space inwhich the vehicle 200 is parked. The power transmission device 10includes an AC/DC converter 11 for rectifying AC voltage supplied froman AC power source 91, an inverter circuit 12, a resonance circuit 13,and a power transmission coil 14. The power transmission device 10further includes a power transmission controller 30.

The power receiving coil 40 includes a power receiving coil 41, aresonance circuit 42, a rectifying smoothing circuit 43, a relay 47, anda battery 44. The power receiving coil 40 further includes a powerreceiving controller 50, an inverter 51 for converting DC voltage outputfrom the battery 44 into AC voltage, and a motor 16 driven by the supplyof the AC voltage output from the inverter 51.

First Embodiment

FIG. 2 is a block diagram showing a configuration of a wireless powersupply system according to a first embodiment of the present invention.As shown in FIG. 2, the wireless power supply system 100 includes thepower transmission device 10 provided on the ground side to transmitelectric power, and the power receiving device 40 that receives thepower transmitted from the power transmission device 10 to supply thepower to the battery 44 (electrical load). Although the presentembodiment exemplifies the battery 44 as an electrical load, the presentinvention is not limited thereto and may use other electrical loads suchas a motor.

The power transmission device 10 includes the AC/DC converter 11 thatconverts AC voltage supplied from the AC power source 91 into DCvoltage, and the inverter circuit 12 that converts the DC voltageconverted by the AC/DC converter 11 into AC voltage having preferredfrequency and amplitude. The power transmission device 10 also includesthe resonance circuit 13 that resonates electric power output from theinverter circuit 12, the power transmission coil 14 that transmits theresonated power, and the power transmission controller 30.

The power transmission device 10 includes an ammeter 21 that detects ACcurrent Iac and a voltmeter 22 that detects AC voltage Vac, the ACcurrent Iac and the AC voltage Vac being supplied to the AC/DC converter11. The power transmission device 10 includes an ammeter 23 that detectsDC current Idc and a voltmeter 24 that detects DC voltage Vdc, the DCcurrent Idc and the DC voltage Vdc being input into the inverter circuit12, and further includes an ammeter 25 that detects AC current I1 and avoltmeter 26 that detects AC voltage V1, the AC current I1 and the ACvoltage V1 being output from the inverter circuit 12. The AC/DCconverter 11 controls a duty ratio when converting the AC voltagesupplied from the AC power source 91 according to a control signaloutput from a PFC controller 39 described below, so as to generate theDC voltage having preferred amplitude.

The inverter circuit 12 includes a plurality of semiconductor switches(such as IGBT) having upper and lower arms, and turns on/off therespective semiconductor switches according to a control signal outputfrom an inverter controller 32 described below, so as to generate the ACvoltage having preferred frequency and amplitude.

The resonance circuit 13 includes a capacitor and an element such as aresistance, and resonates the AC power output from the inverter circuit12 between the resonance circuit 13 and the power transmission coil 14.Namely, the resonance frequency of the power transmission coil 14 andthe capacitor is configured to approximately coincide with the outputfrequency of the inverter circuit 12.

The power transmission coil 14 is, for example, a spiral coil, adisk-shaped coil, a circular coil, or a solenoid coil, provided on theground in the parking space. As shown in FIG. 1, the power transmissioncoil 14 is positioned to be opposed to the power receiving coil 41 whenthe vehicle 200 is parked in a predetermined position in the parkingspace (refer to FIG. 1).

The power transmission controller 30 includes a power factor calculator31, an inverter controller 32, and a control amount calculator 29 (powercontroller). The power transmission controller 30 further includes awireless communication unit 34 (power transmission-side communicationunit) that communicates with the power receiving controller 50, acommunication monitor 33 that monitors communication conditions of thewireless communication unit 34, and a memory 35 that stores powercommand value Pbat* received via wireless communication. The “powercommand value Pbat*” as used herein is a command value of electric powersupplied from the power transmission coil 14, and is transmitted fromthe power receiving device 40.

The power factor calculator 31 obtains, for a predetermined calculationcycle (first cycle), the DC voltage Vdc and the DC current Idc suppliedto the inverter circuit 12, and the AC voltage V1 and the AC current I1output from the inverter circuit 12. The power factor calculator 31calculates a power factor cos θ (second efficiency) of the electricpower output from the inverter 12 based on these Vdc, Idc, V1, and I1.More particularly, the power factor calculator 31 calculates the powerfactor cos θ according to the following formula (1).

cos θ=(Vdc×Idc)/(V1×I1)  (1)

The power factor cos θ used in the current calculation cycle can beobtained by use of Vdc, Idc, V1, and I1 obtained in the previouscalculation cycle. The method of calculating the power factor cos θ isnot limited to the formula (1), and may be any method, such as a methodof measuring a phase difference θ between the voltage V1 and the currentI1 to obtain the power factor cos θ based on the measured phasedifference θ.

The inverter controller 32 controls the inverter circuit 12 to transmitthe electric power corresponding to the power command value Pbat* basedon the power factor cos θ calculated by the power factor calculator 31.

The wireless communication unit 34 implements various kinds of datacommunication with the power receiving controller 50 via a local areanetwork (LAN), for example. The wireless communication unit 34 receivesthe power command value Pbat* transmitted from the power receivingcontroller 50. The wireless communication unit 34 also receives aregulation command signal of charge power transmitted from the powerreceiving controller 50. The wireless communication unit 34 implementsthe data communication for a second cycle longer than the first cyclethat is the calculation cycle of the power factor cos θ calculated bythe power factor calculator 31 as described above. The wirelesscommunication unit 34 thus receives the power command value Pbat*transmitted from the power receiving controller 50 for the second cyclewhen the communication is operated appropriately.

The communication monitor 33 monitors the communication conditions ofthe wireless communication unit 34. The memory 35 stores the powercommand value Pbat* received by the wireless communication unit 34, andoutputs the stored power command value Pbat* to the control amountcalculator 29.

The control amount calculator 29 includes a charge power controller 36,a primary-side current calculator 37, a primary-side current controller38, and a PFC controller 39. The charge power controller 36 obtains thepower command value Pbat* stored in the memory 35 and the power factorcos θ calculated by the power factor calculator 31, so as to correct thepower command value Pbat* by use of the power factor cos θ The chargepower controller 36 outputs the corrected power command value Pbat*′. Inparticular, the charge power controller 36 calculate the corrected powercommand value Pbat*′ according to the following formula (3).

Pbat*′=Pbat*/cos θ  (3)

The primary-side current calculator 37 calculates output current commandvalue Idc* of the AC/DC converter 11 according to the corrected powercommand value Pbat*′ and the DC voltage Vdc output from the AC/DCconverter 11 in the previous calculation cycle.

The primary-side current controller 38 calculates output voltage commandvalue Vdc* of the AC/DC converter 11 according to the output currentcommand value Idc* calculated by the primary-side current calculator 37and the DC current Idc output from the AC/DC converter 11 in theprevious calculation cycle.

The PFC controller 39 determines a duty ratio of conversion in the ACvoltage converted and controlled by the AC/DC converter 11 according tothe DC voltage Vdc detected by the voltmeter 24 in the previouscalculation cycle and the output voltage command value Vdc* output fromthe primary-side current controller 38. The PFC controller 39 obtainsthe current Iac detected by the ammeter 21 (current output from thecurrent power source 91) in the previous cycle and the voltage Vacdetected by the voltmeter [[24]]22 (voltage output from the currentpower source 91), and changes a command value of the duty ratio asappropriate so that the current Iac and the voltage Vac have the samephase. The command value of the duty ratio is output to the AC/DCconverter 11. The AC/DC converter 11 thus controls the output voltageVdc so that the power corresponding to the power command value Pbat* istransmitted from the power transmission coil 14.

The power receiving device 40 includes the power receiving coil 41 thatreceives the power transmitted from the power transmission coil 14 via awireless connection, the resonance circuit 42 that resonates the powerreceived by the power receiving coil 41, and the rectifying smoothingcircuit 43 that converts the AC voltage output from the resonancecircuit 42 into DC voltage and smooths the converted DC voltage. Thepower receiving device 40 also includes the battery 44 that stores theelectric power transmitted from the power transmission device 10, therelay 47 (switching unit) that switches connection and disconnectionbetween the rectifying smoothing circuit 43 and the battery 44, and thepower receiving controller 50. The power receiving device 40 furtherincludes an ammeter 45 that detects current Ibat and a voltmeter 46 thatdetects voltage Vbat, the current Ibat and the voltage Vbat being outputfrom the rectifying smoothing circuit 43.

The power receiving coil 41 is, for example, a spiral coil, adisk-shaped coil, a circular coil, or a solenoid coil, mounted on thebottom of the vehicle. The power receiving coil 41 is positioned to beopposed to the power transmission coil 14 provided on the ground in apredetermined charge position in the parking space when the vehicle isparked in the charge position.

The resonance circuit 42 includes a capacitor and an element such as aresistance, and resonates the AC power received by the power receivingcoil 41. Namely, the resonance frequency of the circuit including thepower receiving coil 41 and the capacitor is configured to approximatelycoincide with the frequency of the AC power transmitted from the powertransmission coil 14.

The rectifying smoothing circuit 43 includes a rectifying circuit suchas a diode bridge circuit, and a smoothing circuit including acapacitor. The rectifying smoothing circuit 43 rectifies the AC voltageoutput from the resonance circuit 42, and further smooths and suppliesthe AC voltage to the battery 44.

The relay 47 supplies the power received by the power receiving coil 41to the battery 44 (electrical load) once connected, and stops supplyingthe power to the battery 44 once disconnected. The relay 47 thus servesas a switching unit for switching between the operation of supplying thepower received by the power receiving coil 41 to the electrical load(the battery 44) and the operation of stopping the supply to theelectrical load.

The power receiving controller 50 includes a wireless communication unit51 (power receiving-side communication unit) that communicates with thewireless communication unit 34 provided in the power transmissioncontroller 30 in a wireless manner such as LAN communication, acommunication monitor 52 that monitors communication conditions of thewireless communication unit 51, a CAN communication unit 53, anefficiency calculator 55, and a relay controller 54 (switchingcontroller).

The CAN communication unit 53 is connected to various types ofcontrollers, such as a battery controller 56 and a vehicle controller57, through a BUS line 58 to implement data communication therebetweenvia a controller area network (CAN). The battery controller 56 generatespower command value Pbat* and output it to the CAN communication unit 53through the BUS line 58.

The efficiency calculator 55 obtains the power command value Pbat*transmitted through the CAN communication unit 53, and further obtainsthe current Ibat detected by the ammeter 45 and the voltage Vbatdetected by the voltmeter 46, so as to calculate power transmissionefficiency η (first efficiency) of the electric power transmittedbetween the power transmission device 10 and the power receiving device40 according to the obtained data. In particular, the efficiencycalculator 55 calculates transmitted power Pbat by multiplying thecurrent Ibat and the voltage Vbat together, so as to obtain the powertransmission efficiency η according to the following formula (2).

η=Pbat/Pbat*=(Ibat×Vbat)/Pbat*  (2)

When the power transmission efficiency η calculated according to theformula (2) falls to predetermined threshold efficiency ηth or less, theefficiency calculator 55 outputs a cut-off command signal to the relaycontroller 54. The efficiency calculator 55 further outputs a regulationcommand signal of charge power. The regulation command signal istransmitted to the power transmission device 10 via the wirelesscommunication unit 51.

When the relay controller 54 receives the cut-off command signalsupplied from the efficiency calculator 55, the relay controller 54 cutsoff the relay 47, and stops supplying the power to the battery 44. Moreparticularly, when the power transmission efficiency η calculated by theefficiency calculator 55 falls to the threshold efficiency ηth or less,the relay controller 54 determines that a problem is caused between thepower transmission coil 14 and the power receiving coil 41 for somereason, and stops supplying the power to the battery 44.

In the wireless power supply system 100 according to the firstembodiment, when the power factor cos θ calculated by the power factorcalculator 31 falls below the predetermined threshold power factor, thecorrected power command value Pbat*′ calculated by the charge powercontroller 36 is regulated, so that the power transmitted from the powertransmission device 10 to the power receiving device 40 is regulated. Asused herein, the term “regulate” includes the meanings of “reduce” and“reduce to zero”.

Since the relay 47 is cut off when the power transmission efficiency ηcalculated by the efficiency calculator 55 falls to the thresholdefficiency ηth or less, the circuit on the power receiving device 40side including the power receiving coil 41 and the battery 44 is open asviewed from the power transmission coil 14 side. As a result, theimpedance of the entire circuit, including the power transmission coil14, the power receiving coil 41, and the battery 44 increases, and thephase difference between the current I1 and the voltage V1 output fromthe inverter circuit 12 increases. Accordingly, the transmitted power isregulated since the power factor cos θ decreases. Further, theregulation command signal of the charge power is transmitted to thepower transmission controller 30 through the wireless communication unit51 when the power transmission efficiency η falls to the thresholdefficiency ηth or less, and the output power is regulated accordingly.

Next, the operation of the wireless power supply system 100 according tothe first embodiment is described below with reference to the flowchartsshown in FIG. 3 and FIG. 4. FIG. 3 is a flowchart showing a processingprocedure implemented by the power transmission controller 30. In FIG.3, the processing from step S11 to step S15 is executed in thecalculation cycle in the first process after the calculation starts, andthe following processing from step S16 is executed in the calculationcycle in the second process and repeated in the subsequent cycles.

First, in step S11, the wireless communication unit 34 communicates withthe wireless communication unit 51 of the power receiving controller 50in a wireless manner such as LAN communication. The wirelesscommunication is carried out for the second cycle, as described above.In step S12, the wireless communication unit 34 receives the powercommand value Pbat* transmitted from the power receiving controller 50.In particular, the power command value Pbat* output from the batterycontroller 56 shown in FIG. 2 is transmitted from the wirelesscommunication unit 51 and received by the wireless communication unit34.

In step S13, the control amount calculator 29 implements an initialsetting to set the output voltage command value Vdc* such that theoutput voltage Vdc output from the AC/DC converter 11 has the minimumvalue.

In step S14, the inverter controller 32 sets a drive frequency and adrive duty ratio of the inverter circuit 12 each to a predeterminedconstant value to drive the inverter circuit 12. In step S15, the powertransmission coil 14 starts excitation. Namely, the AC current isapplied to the power transmission coil 14 so as to generate magneticflux.

In step S16, the voltmeter 22, the ammeter 21, the voltmeter 24, theammeter 23, the voltmeter 26, and the ammeter 25 detect the voltage Vac,the current Iac, the voltage Vdc, the current Idc, the voltage V1, andthe current I1, respectively. The voltage Vac and the current Iac aresupplied to the control amount calculator 29, the voltage Vdc and thecurrent Idc are supplied to the control amount calculator 29 and thepower factor calculator 31, and the voltage V1 and the current I1 aresupplied to the power factor calculator 31.

In step S17, the power factor calculator 31 calculates the power factorcos θ of the power output from the inverter circuit 12, according to thefollowing formula (1).

cos θ=(Vdc×Idc)/(V1×I1)  (1)

In step S18, the control amount calculator 29 corrects the power commandvalue Pbat*. The control amount calculator 29 obtains the correctedpower command value Pbat*′ according to the following formula (3).

Pbat*′=Pbat*/cos θ  (3)

In step S19, the control amount calculator 29 calculates the voltagecontrol amount Vdc* according to the block diagram shown in FIG. 5. Asshown in FIG. 5, the charge power controller 36 corrects the powercommand value Pbat* based on the power factor cos θ to generate thecorrected power command value Pbat*′. The primary-side currentcalculator 37 shown in FIG. 5 calculates the current command value Idc*by dividing the corrected power command value Pbat*′ by the voltage Vdcdetected in the previous calculation cycle.

A subtractor 18 subtracts the current Idc detected in the previouscalculation cycle from the current command value Idc*. The primary-sidecurrent controller 38 then obtains the voltage command value Vdc* by PIcontrol based on the subtraction result. The primary-side currentcontroller 38 outputs the obtained voltage command value Vdc* to the PFCcontroller 39. The PFC controller 39 controls the duty ratio so that theoutput voltage of the AC/DC converter 11 corresponds to the voltagecommand value Vdc*. Accordingly, the power corresponding to thecorrected power command value Pbat*′ is transmitted from the powertransmission coil 14 to the power receiving coil 41. In step S20 shownin FIG. 3, the voltage command value Vdc* is calculated, as describedabove. The power controlled according to the power factor cos θ is thustransmitted from the power transmission device 10 to the power receivingdevice 40.

In step S21, the control amount calculator 29 determines whether thepower factor cos θ calculated by the power factor calculator 31 exceedsa threshold power factor. When the power factor cos θ exceeds thethreshold power factor (YES in step S21), the process proceeds to stepS22. When the power factor cos θ is less than or equal to the thresholdpower factor (NO in step S21), the process proceeds to step S23.

In step S22, the control amount calculator 29 determines whether thepower transmission regulation command is transmitted from the powerreceiving controller 50. The process proceeds to step S23 when the powertransmission regulation command is transmitted (YES in step S22), andthe process returns to step S16 when the power transmission regulationcommand is not yet transmitted (NO in step S22).

In step S23, the control amount calculator 29 regulates the powersupplied to the battery 44. In particular, the control amount calculator29 regulates the voltage Vdc output from the AC/DC converter 11. Whenthe power factor cos θ falls to the threshold power factor or less, orwhen the power transmission regulation command is received, the powertransmitted from the power transmission coil 14 is regulated. Theprocess in step S21 proceeds to step S23 when the power factor cos θ isthe threshold power factor or less, as described above. However, thepower transmission is occasionally not stabilized when the power factorcos θ is closer to the maximum value “1”. The power factor cos θ maytherefore be assigned an upper limit, so that the process in step S21proceeds to step S23 also when the power factor cos θ exceeds the upperlimit.

Next, a processing procedure implemented by the power receivingcontroller 50 is described below with reference to the flowchart shownin FIG. 4. The processing in step S31 and step S32 is executed in thecalculation cycle in the first process after the calculation starts, andthe following processing from step S33 is executed in the calculationcycle in the second process and repeated in the subsequent cycles.

First, in step S31, the wireless communication unit 51 communicates withthe wireless communication unit 34 of the power transmission controller30 in a wireless manner such as LAN communication. The wirelesscommunication is carried out for the second cycle, as described above.In step S32, the wireless communication unit 51 transmits the powercommand value Pbat* output from the battery controller 56 to the powertransmission controller 30 via wireless communication.

In step S33, the efficiency calculator 55 obtains the voltage Vbatdetected by the voltmeter 46 and the current Ibat detected by theammeter 45. In step S34, the efficiency calculator 55 calculates thepower Pbat supplied to the battery 44 by multiplying the voltage Vbatand the current Ibat together. The efficiency calculator 55 furthercalculates the power transmission efficiency η of the power according tothe following formula (2), based on the power Pbat and the power commandvalue Pbat*.

η=Pbat/Pbat*=(Ibat×Vbat)/Pbat*  (2)

In step S35, the efficiency calculator 55 determines whether theefficiency η calculated according to the formula (2) exceeds thepredetermined threshold efficiency ηth. When the efficiency η exceedsthe predetermined threshold efficiency ηth, that is, η>ηth (YES in stepS35), the process returns to step S33. When the efficiency η is lessthan or equal to the predetermined threshold efficiency ηth, that is,η≦ηth (NO in step S35), the efficiency calculator 55 outputs the cut-offcommand signal to the relay controller 54 in step S36. The relaycontroller 54 then cuts off the relay 47. The transmitted power is thusregulated once the relay 47 is cut off, since the phase differencebetween the voltage V1 and the current I1 output from the invertercircuit 12 increases, and the power factor cos θ decreases.

The wireless communication unit 51 communicates with the wirelesscommunication unit 34 of the power transmission controller 30 in stepS37, and transmits the power transmission regulation command in stepS38. The transmitted power transmission regulation command is detectedin step S22 in FIG. 3, and the charge power is regulated in step S23.The power transmitted from the power transmission coil 14 can thereforebe regulated when the power transmission efficiency η of the powertransmitted from the power transmission coil 14 to the power receivingcoil 41 is decreased.

In the wireless power supply system 100 according to the firstembodiment, the power factor calculator 31 calculates the power factorcos θ of the power output from the inverter circuit 12, and the voltageVdc output from the AC/DC converter 11 is regulated when the powerfactor cos θ falls to the predetermined threshold power factor or less.The transmitted power can therefore be regulated for the first cycleshorter than the second cycle which is the communication cycle of thewireless communication unit 34 when the power factor cos θ is decreased.Accordingly, unnecessary power transmission can immediately besuppressed, so that trouble with the system such as heat generation canbe prevented, when the positions of the power transmission coil 14 andthe power receiving coil 41 are shifted from each other for some reason,such as a collision of the vehicle with another, or contrived movementof the vehicle. Further, the power transmission can surely be regulatedwhen the wireless communication between the wireless communication unit34 and the wireless communication unit 51 is interrupted, since areduction of the power factor cos θ is detected only through thecalculation by the power transmission device 10 to regulate thetransmitted power, without the need of data transmitted from the powerreceiving controller 50.

Further, a reduction of the power transmission efficiency η can beanalyzed by use of the power factor cos θ with high accuracy, ascompared with a case in which a level of the current I1 output from theinverter circuit 12 (current supplied to the power transmission coil 14)is detected for analyzing the power transmission efficiency. Since thecurrent I1 includes both an active component and a reactive component,the level of the active component and the level of the reactivecomponent cannot be analyzed independently. The power transmissionefficiency by use of the power factor cos θ can be analyzed moreaccurately because a change of the active component is reflected.

Since the relay 47 is cut off when the power transmission efficiency ηcalculated by the efficiency calculator 55 falls to the thresholdefficiency ηth or less, the circuit on the power receiving device 40side including the power receiving coil 41 and the battery 44 is open asviewed from the power transmission coil 14 side. As a result, theimpedance of the entire circuit, including the power transmission coil14, the power receiving coil 41, and the battery 44 increases, and thephase difference between the current I1 and the voltage V1 output fromthe inverter circuit 12 increases. Accordingly, the transmitted power isregulated since the power factor cos θ decreases. Namely, thetransmitted power can be regulated when the wireless communicationbetween the wireless communication unit 34 and the wirelesscommunication unit 51 is interrupted, and when a problem with the powertransmission efficiency η is detected by the power receiving controller50.

When a reduction of the efficiency η is detected by the power receivingdevice 40, the power transmission regulation command is transmitted tothe power transmission controller 30 via wireless communication, so thatthe transmitted power is regulated. The power transmitted from the powertransmission device 10 can therefore be regulated more accurately due tothe power transmission regulation command even when the power factor cosθ is not reduced although a problem is caused.

Modified Example of First Embodiment

The first embodiment exemplified the case in which the power factorcalculator 31 calculates the power factor cos θ to regulate thetransmitted power when the power factor cos θ falls to the thresholdpower factor or less. In the modified example, a reduction of the powertransmission efficiency is detected by use of the current I1 output fromthe inverter circuit 12 instead of the power factor cos θ. The currentI1 increases as the transmission efficiency of the electric powertransmitted from the power transmission coil 14 decreases. When acoupling coefficient between the power transmission coil 14 and thepower receiving coil 41 is defined “α”, the current I1 and the couplingcoefficient α are correlated with each other. In particular, as thecoupling coefficient α decreases, the current I1 increases.

In the modified example, a map indicating the correlation between thecurrent I1 and the coupling coefficient α is preliminarily stored, andthe coupling coefficient α is computed according to the map when thecurrent I1 is detected, so that the transmitted power is regulated whenthe coupling coefficient α falls to a predetermined threshold level.Accordingly, unnecessary power transmission can immediately besuppressed, so that trouble with the system such as heat generation canbe prevented when the positions of the power transmission coil 14 andthe power receiving coil 41 are shifted from each other, as in the caseof the first embodiment.

Second Embodiment

A second embodiment of the present invention is described below. FIG. 6is a block diagram showing a configuration of a wireless power supplysystem according to the second embodiment. As shown in FIG. 6, thewireless power supply system 101 according to the second embodimentdiffers from the wireless power supply system 100 shown in FIG. 2 in theconfiguration of a power transmission controller 30 a provided in apower transmission device 10 a. The other elements are the same as thoseshown in FIG. 2 and therefore denoted by the same reference numerals,and detail descriptions thereof are not repeated below.

The power transmission controller 30 a includes the wirelesscommunication unit 34, the communication monitor 33, the memory 35, thecontrol amount calculator 29, and the inverter controller 32 forcontrolling the inverter circuit 12, as in the case shown in FIG. 2. Thepower transmission controller 30 a further includes an overcurrentdetector 71 that detects an overcurrent based on the current I1 detectedby the ammeter 25. The power transmission controller 30 a does notinclude the power factor calculator 31 shown in FIG. 2.

The wireless communication unit 34 communicates with the wirelesscommunication unit 51, receives the power command value Pbat*, andreceives the power transmission efficiency η transmitted from thewireless communication unit 51. The memory 35 stores the power commandvalue Pbat* and the power transmission efficiency η received by thewireless communication unit 34.

The control amount calculator 29 includes the charge power controller36, the primary-side current calculator 37, the primary-side currentcontroller 38, and the PFC controller 39, as in the case shown in FIG.2.

The charge power controller 36 obtains the power command value Pbat* andthe power transmission efficiency η output from the memory 35, andcorrects the power command value Pbat* according to the powertransmission efficiency η. The charge power controller 36 outputs thecorrected power command value Pbat*′. In particular, the charge powercontroller 36 outputs the corrected power command value Pbat*′calculated according to the following formula (4).

Pbat*′=Pbat*/η  (4)

The configurations of the primary-side current calculator 37, theprimary-side current controller 38, and the PFC controller 39 are thesame as those described in the first embodiment, and detailsdescriptions thereof are not repeated below.

The overcurrent detector 71 obtains the current I1 output from theinverter 12 for the first cycle, and detects an overcurrent once thecurrent I1 exceeds a predetermined threshold current. The overcurrentdetector 71 outputs an overcurrent detection signal to the PFCcontroller 39. The PFC controller 39 regulates the output voltage of theAC/DC converter 11 when the overcurrent is detected by the overcurrentdetector 71.

The power receiving controller 50 outputs the power transmissionefficiency η calculated by the efficiency calculator 55 to the wirelesscommunication unit 51 through the CAN communication unit 53. Thewireless communication unit 51 transmits the power transmissionefficiency η to the power transmission controller 30 a. The powertransmission efficiency η can be calculated according to the followingformula (2), as described in the first embodiment.

η=Pbat/Pbat*=(Ibat×Vbat)/Pbat*  (2)

Next, the operation of the wireless power supply system 101 according tothe second embodiment configured as described above is described belowwith reference to the flowcharts shown in FIG. 7 and FIG. 8. FIG. 7 is aflowchart showing a processing procedure implemented by the powertransmission controller 30 a. In FIG. 7, the processing from step S41 tostep S45 is executed in the calculation cycle in the first process afterthe calculation starts, and the following processing from step S46 isexecuted in the calculation cycle in the second process and repeated inthe subsequent cycles. The processing from step S41 to step S45 is thesame as that from step S11 to step S15 shown in FIG. 3, and detaildescriptions thereof are not repeated below.

In step S46, the communication monitor 33 determines whether thecommunication cycle between the wireless communication unit 34 and thewireless communication unit 51 of the power receiving controller 50 isthe second cycle. The process proceeds to step S47 when thecommunication cycle is the second cycle (YES in step S46), and theprocess proceeds to step S50 when the communication cycle is not thesecond cycle (NO in step S46).

In step S47, the wireless communication unit 34 communicates with thewireless communication unit 51 in a wireless manner. In step S48, thewireless communication unit 34 receives the power transmissionefficiency η transmitted from the power receiving device 50. In stepS49, the power transmission efficiency η stored in the memory 35 isupdated.

In step S50, the voltmeter 22, the ammeter 21, the voltmeter 24, theammeter 23, the voltmeter 26, and the ammeter 25 detect the voltage Vac,the current Iac, the voltage Vdc, the current Idc, the voltage V1, andthe current I1, respectively. The voltage Vac, the current Iac, thevoltage Vdc, and the current Idc are supplied to the control amountcalculator 29, and the current I1 is supplied to the overcurrentdetector 71.

In step S51, the control amount calculator 29 corrects the power commandvalue Pbat* by use of the power transmission efficiency η. The controlamount calculator 29 obtains the corrected power command value Pbat*′according to the following formula (4).

Pbat*′=Pbat*/η  (4)

In step S52, the control amount calculator 29 calculates the voltagecontrol amount Vdc* according to the block diagram shown in FIG. 5, asdescribed above. In step S53, the control amount calculator 29determines the control amount of the voltage Vdc. This calculationmethod is the same as that described in the first embodiment, and detaildescriptions thereof are omitted here. According to this control, theelectric power corresponding to the power transmission efficiency η istransmitted from the power transmission device 10 a to the powerreceiving device 40.

In step S54, the control amount calculator 29 determines whether anovercurrent is detected by the overcurrent detector 71. As describedbelow, the current I1 output from the inverter circuit 12 is recognizedas an overcurrent when a reduction of the power transmission efficiencyη is detected by the power receiving controller 50, and the relay 47 isthus cut off. In other words, the cut-off state of the relay 47 can beconfirmed depending on whether the output current I1 is the overcurrent.The process proceeds to step S55 when the overcurrent is not detected(NO in step S54), and the process proceeds to step S56 when theovercurrent is detected (YES in step S54).

In step S55, the control amount calculator 29 determines whether thepower transmission regulation command is transmitted from the powerreceiving controller 50. The process proceeds to step S56 when the powertransmission regulation command is transmitted (YES in step S55), andthe process returns to step S46 when the power transmission regulationcommand is not yet transmitted (NO in step S55).

In step S56, the control amount calculator 29 regulates the electricpower supplied to the battery 44. In particular, the control amountcalculator 29 regulates the output voltage of the AC/DC converter 11, soas to regulate the power transmitted from the power transmission coil 14to the power receiving coil 41. Namely, the overcurrent is detected bythe overcurrent detector 71 when the relay 47 is cut off, and thetransmitted power is regulated accordingly.

Next, a processing procedure implemented by the power receivingcontroller 50 is described below with reference to the flowchart shownin FIG. 8. The processing in step S61 and step S62 is executed in thecalculation cycle in the first process after the calculation starts, andthe following processing from step S63 is executed in the calculationcycle in the second process and repeated in the subsequent cycles. Theprocessing in step S61 and step S62 is the same as that in step S31 andstep S32 shown in FIG. 4, and detail descriptions thereof are notrepeated below.

In step S63, the efficiency calculator 55 obtains the voltage Vbatdetected by the voltmeter 46 and the current Ibat detected by theammeter 45. In step S64, the efficiency calculator 55 calculates thepower Pbat supplied to the battery 44 by multiplying the voltage Vbatand the current Ibat together. The efficiency calculator 55 furthercalculates the power transmission efficiency η according to thefollowing formula (2), based on the power Pbat and the power commandvalue Pbat*.

η=Pbat/Pbat*=(Ibat×Vbat)/Pbat*  (2)

In step S65, the communication monitor 52 determines whether thecommunication cycle between the wireless communication unit 51 and thewireless communication unit 34 of the power transmission controller[[30]]30 a is the second cycle. The process proceeds to step S66 whenthe communication cycle is the second cycle (YES in step S65), and theprocess proceeds to step S68 when the communication cycle is not thesecond cycle (NO in step S65).

In step S66, the wireless communication unit 51 communicates with thewireless communication unit 34 of the power transmission controller 30 ain a wireless manner. In step S67, the wireless communication unit 51transmits the power transmission efficiency η to the power transmissioncontroller 30 a. The power transmission efficiency η is received by thewireless communication unit 34 in step S48 in FIG. 7, and stored in thememory 35 in step S49. Accordingly, the power transmission efficiency ηstored in the memory 35 is updated every time the second cycle haspassed.

In step S68, the efficiency calculator 55 determines whether the powertransmission efficiency η exceeds the predetermined threshold efficiencyηth. When the power transmission efficiency η exceeds the predeterminedthreshold efficiency ηth, that is, η>ηth (YES in step S68), the processreturns to step S63. When the efficiency η is less than or equal to thepredetermined threshold efficiency ηth, that is, η≦ηth (NO in step S68),the efficiency calculator 55 outputs the cut-off command signal to therelay controller 54 in step S69. The relay controller 54 then cuts offthe relay 47. Accordingly, the transmitted power is regulated, since thecurrent I1 output from the inverter circuit 12 results in theovercurrent when the relay 47 is cut off.

The wireless communication unit 51 further communicates with thewireless communication unit 34 of the power transmission controller 30 ain step S70, and transmits the power transmission regulation command instep S71. The transmitted power transmission regulation command isdetected in step S55 in FIG. 7, and the charge power is regulated instep S56. The power transmitted from the power transmission coil 14 cantherefore be regulated when the power transmission efficiency η of thepower from the power transmission coil 14 to the power receiving coil 41is decreased.

In the wireless power supply system 101 according to the secondembodiment, when the power transmission efficiency η calculated by thepower factor calculator 55 falls to the predetermined thresholdefficiency ηth or less, the relay 47 is cut off, so that the circuit onthe power receiving device 40 side including the power receiving coil 41and the battery 44 is open as viewed from the power transmission coil 14side. As a result, the impedance of the entire circuit, including thepower transmission coil 14, the power receiving coil 41, and the battery44 increases, and the current I1 output from the inverter circuit 12increases to result in the overcurrent. When the overcurrent detector 71detects the overcurrent, the voltage Vdc output from the AC/DC converter11 is regulated. Accordingly, the power transmitted from the powertransmission coil 14 to the power receiving coil 41 is regulated. Sincethe detection of the overcurrent is carried out for the first cycle, thetransmitted power can be regulated immediately.

Accordingly, unnecessary power transmission can immediately besuppressed, so that trouble with the system such as heat generation canbe prevented, when the positions of the power transmission coil 14 andthe power receiving coil 41 are shifted from each other for some reason,such as a collision of the vehicle with another, or contrived movementof the vehicle. Further, the transmitted power can be regulated alsowhen the wireless communication between the wireless communication unit51 and the wireless communication unit 34 is interrupted.

When a reduction of the power transmission efficiency η is detected bythe power receiving controller 50, the power transmission regulationcommand is transmitted to the power transmission controller 30 a viawireless communication for the second cycle, so that the transmittedpower is regulated. Even when the relay 47 is not cut off in spite ofthe reduction of the power transmission efficiency η, the powertransmitted from the power transmission coil 14 can be regulated due tothe power transmission regulation command, so that unnecessary powertransmission can more surely be suppressed.

The power transmission controller 30 a corrects the power command valuePbat* to obtain the corrected power command value Pbat*′ according tothe power transmission efficiency η transmitted from the power receivingcontroller 50, and further calculates the voltage command value Vdc* byuse of the corrected power command value Pbat*′, so that the transmittedpower can be controlled depending on the power transmission efficiencyη. When the current I1 output from the inverter circuit 12 increases toresult in the overcurrent and detected by the overcurrent detector 71,the overcurrent detection signal may be output to the invertercontroller 32 instead of the PFC controller 39, so as to directly andforcibly stop the inverter circuit 12.

Modified Example of Second Embodiment

A modified example of the second embodiment is described below. Thesecond embodiment exemplified the case in which the power receivingcontroller 50 calculates the power transmission efficiency η, andtransmits the calculated power transmission efficiency η to the powertransmission controller [[30]]30 a. In the wireless power supply systemaccording to the modified example, the power receiving controller 50transmits data of the current that detected by the ammeter 45 and thevoltage Vbat detected by the voltmeter 46 to the power transmissioncontroller 30 a, and the power transmission controller 30 a thencalculates the power transmission efficiency η. The calculation is thusexecuted according to the following formula (4), as used in step S51shown in FIG. 7.

Pbat*′=Pbat*/η  (4)

The wireless power supply system according to the modified example canachieve the same effects as the wireless power supply system accordingto the second embodiment descried above.

Third Embodiment

A third embodiment of the present invention is described below. FIG. 9is a block diagram showing a configuration of a wireless power supplysystem 101 according to the third embodiment. The wireless power supplysystem 101 shown in FIG. 9 has the same configuration as that shown inFIG. 6, but differs in that the power transmission efficiency ηcalculated by the efficiency calculator 55 is not transmitted to thepower transmission controller 30 a. The same elements are denoted by thesame reference numerals, and detail descriptions thereof are notrepeated below.

The operation of the wireless power supply system 101 according to thethird embodiment is described below with reference to the flowchartsshown in FIG. 10 and FIG. 11. FIG. 10 is a flowchart showing aprocessing procedure implemented by the power transmission controller 30a. In FIG. 10, the processing from step S81 to step S85 is executed inthe calculation cycle in the first process after the calculation starts,and the following processing from step S86 is executed in thecalculation cycle in the second process and repeated in the subsequentcycles. The processing from step S81 to step S85 is the same as thatfrom step S41 to step S45 shown in FIG. 7, and detail descriptionsthereof are not repeated below.

In step S86, the voltmeter 22, the ammeter 21, the voltmeter 24, theammeter 23, the voltmeter 26, and the ammeter 25 detect the voltage Vac,the current Iac, the voltage Vdc, the current Idc, the voltage V1, andthe current I1, respectively. The voltage Vac, the current Iac, thevoltage Vdc, and the current Idc are supplied to the control amountcalculator 29, and the current I1 is supplied to the overcurrentdetector 71.

In step S87, the control amount calculator 29 calculates the voltage Vdcoutput from the AC/DC converter 11 based on the power command valuePbat*, so that the current Idc on the primary side of the invertercircuit 12 is constant. In step S88, the control amount calculator 29determines the control amount of the voltage Vdc.

The processing from step S89 to step S91 is the same as that from stepS54 to step S56 shown in FIG. 7, and detail descriptions thereof are notrepeated below. Through the processing shown in FIG. 10, the overcurrentis detected by the overcurrent detector 71 when the relay 47 is cut off,and the transmitted power is regulated accordingly.

Next, a processing procedure implemented by the power receivingcontroller 50 is described below with reference to the flowchart shownin FIG. 11. The processing in step S101 and step S102 is executed in thecalculation cycle in the first process after the calculation starts, andthe following processing from step S103 is executed in the calculationcycle in the second process and repeated in the subsequent cycles. Theprocessing from step S101 to step S104 is the same as that from step S61to step S64 shown in FIG. 8, and detail descriptions thereof are notrepeated below.

When the power transmission efficiency η is calculated in step S104, theefficiency calculator 55 determines in step S105 whether the powertransmission efficiency η exceeds the predetermined threshold efficiencyηth. When the power transmission efficiency η exceeds the predeterminedthreshold efficiency ηth, that is, η>ηth (YES in step S105), the processreturns to step S103. When the power transmission efficiency η is lessthan or equal to the predetermined threshold efficiency ηth, that is,η≦ηth (NO in step S105), the efficiency calculator 55 outputs thecut-off command signal to the relay controller 54 in step S106. Therelay controller 54 then cuts off the relay 47. Accordingly, thetransmitted power is regulated, since the current I1 output from theinverter circuit 12 results in the overcurrent when the relay 47 is cutoff.

The wireless communication unit 51 communicates with the wirelesscommunication unit 34 of the power transmission controller 30 a in stepS107, and transmits the power transmission regulation command in stepS108. The transmitted power transmission regulation command is detectedin step S90 in FIG. 10, and the charge power is regulated in step S91.More particularly, when the power transmission efficiency η of the powertransmitted from the power transmission coil 14 to the power receivingcoil 41 is decreased, the power transmission regulation command istransmitted for the second cycle, so that the power transmitted from thepower transmission coil 14 is regulated.

In the wireless power supply system 101 according to the thirdembodiment, when the power transmission efficiency η calculated by thepower factor calculator 55 falls to the predetermined thresholdefficiency ηth or less, the relay 47 is cut off. The circuit on thepower receiving device 40 side including the power receiving coil 41 andthe battery 44 is thus open as viewed from the power transmission coil14 side. As a result, the impedance of the entire circuit, including thepower transmission coil 14, the power receiving coil 41, and the battery44 increases, and the current I1 output from the inverter circuit 12increases to result in the overcurrent. When the overcurrent detector 71detects the overcurrent, the voltage Vdc output from the AC/DC converter11 is regulated. Accordingly, the transmitted power from the powertransmission coil 14 to the power receiving coil 41 is regulated. Sincethe detection of the overcurrent is carried out for the first cycle, thetransmitted power can be regulated immediately.

Accordingly, unnecessary power transmission can immediately besuppressed, so that trouble with the system such as heat generation canbe prevented, when the positions of the power transmission coil 14 andthe power receiving coil 41 are shifted from each other for some reason,such as a collision of the vehicle with another, or contrived movementof the vehicle. Further, the transmitted power can be regulated alsowhen the wireless communication between the wireless communication unit51 and the wireless communication unit 34 is interrupted.

When a reduction of the power transmission efficiency η is detected bythe power receiving controller 50, the power transmission regulationcommand is transmitted to the power transmission controller 30 a viawireless communication for the second cycle, so that the transmittedpower is regulated. Even when the relay 47 is not cut off in spite ofthe reduction of the power transmission efficiency η, the powertransmitted from the power transmission coil 14 is regulated due to thepower transmission regulation command, so that unnecessary powertransmission can more surely be suppressed.

Since the power transmission controller 30 a does not correct but keepsthe command value Pbat* constant regardless of the change of the powertransmission efficiency η, the calculation load can be reduced ascompared with the case described in the second embodiment.

Fourth Embodiment

A fourth embodiment of the present invention is described below. FIG. 12is a block diagram showing a configuration of a wireless power supplysystem according to the fourth embodiment. The wireless power supplysystem 102 shown in FIG. 12 differs from the wireless power supplysystem 100 shown in FIG. 2 in that the efficiency calculator 55 of thepower receiving controller 50 outputs the power transmission efficiencyη to the CAN communication unit 53, and the power transmissionefficiency η is then transmitted from the wireless communication unit51, and further in that the power transmission efficiency η received bythe wireless communication unit 34 is stored in the memory 35, and thecontrol amount calculator 29 calculates the control amount of thevoltage Vdc by use of the power transmission efficiency η. The otherelements are the same as those shown in FIG. 2 and therefore denoted bythe same reference numerals, and detail descriptions thereof are notrepeated below. The communication between the respective wirelesscommunication units 51 and 34 is carried out for the second cycle, as inthe case of the first embodiment. The power factor cos θ is calculatedby the power factor calculator 31 for the first cycle shorter than thesecond cycle.

The operation of the wireless power supply system 102 according to thefourth embodiment is described below with reference to the flowchartsshown in FIG. 13 and FIG. 14. In FIG. 13, the processing from step S111to step S115 is executed in the calculation cycle in the first processafter the calculation starts, and the following processing from stepS116 is executed in the calculation cycle in the second process andrepeated in the subsequent cycles. The processing from step S111 to stepS117 is the same as that from step S11 to step S17 shown in FIG. 3, anddetail descriptions thereof are not repeated below.

When the power factor cos θ is calculated in step S117, thecommunication monitor 33 determines in step S118 whether thecommunication cycle between the wireless communication unit 34 and thewireless communication unit 51 of the power receiving controller 50 isthe second cycle. The process proceeds to step S119 when thecommunication cycle is the second cycle (YES in step S118), and theprocess proceeds to step S123 when the communication cycle is not thesecond cycle (NO in step S118).

In step S119, the wireless communication unit 34 communicates with thewireless communication unit 51. In step S120, the wireless communicationunit 34 receives the power transmission efficiency η. In step S121, thememory 35 updates the power transmission efficiency η with newlyreceived data. Since the communication by the wireless communicationunit 34 is carried out in every second cycle, the power transmissionefficiency η is updated by the memory 35 every time the second cycle haspassed.

In step S122, the control amount calculator 29 corrects the powercommand value Pbat* by use of the power transmission efficiency η. Thecontrol amount calculator 29 obtains the corrected power command valuePbat*′ according to the following formula (4).

Pbat*′=Pbat*/η  (4)

In step S123, the control amount calculator 29 corrects the powercommand value Pbat* by use of the power factor cos θ. The control amountcalculator 29 obtains the corrected power command value Pbat*′ accordingto the following formula (3).

Pbat*′=Pbat*/cos θ  (3)

When the communication cycle between the wireless communication unit 34and the wireless communication unit 51 of the power receiving controller50 is the second cycle, the control amount calculator 29 calculates thecorrected power command value Pbat*′ by use of the power transmissionefficiency η (first efficiency) transmitted from the power receivingcontroller 50. When the communication cycle is not the second cycle, thecontrol amount calculator 29 calculates the corrected power commandvalue Pbat*′ by use of the power factor cos θ (second efficiency)calculated by the power transmission controller 30 b. The process thenproceeds to step S124. The processing from step S124 to step S128 is thesame as that from step S19 to step S23 shown in FIG. 3, and detaildescriptions thereof are not repeated below.

Next, a processing procedure implemented by the power receivingcontroller 50 is described below with reference to the flowchart shownin FIG. 14. The processing in step S131 and step S132 is executed in thecalculation cycle in the first process after the calculation starts, andthe following processing from step S133 is executed in the calculationcycle in the second process and repeated in the subsequent cycles. Theprocessing from step S131 to step S134 is the same as that from step S31to step S34 shown in FIG. 4, and detail descriptions thereof are notrepeated below.

When the power transmission efficiency η is calculated by the efficiencycalculator 55 in step S134, the communication monitor [[33]]52determines in step S135 whether the communication cycle between thewireless communication unit [[34]]51 and the wireless communication unit[[51]]34 of the power transmission controller [[50]]30 b is the secondcycle. The process proceeds to step S136 when the communication cycle isthe second cycle (YES in step S135), and the process proceeds to stepS138 when the communication cycle is not the second cycle (NO in stepS135).

In step S136, the wireless communication unit 51 communicates with thewireless communication unit 34 of the power transmission controller 30b. In step S137, the wireless communication unit 51 transmits the powertransmission efficiency η. The process then proceeds to step S138. Theprocessing from step S138 to step S141 is the same as that from step S35to step S38 shown in FIG. 4, and detail descriptions thereof are notrepeated below.

The processing is thus implemented such that the charge power Pbat ofthe battery 44 is calculated by use of the voltage Vbat and the currentIbat, and the power transmission efficiency η is obtained by the ratioof the charge power Pbat to the power command value Pbat*. The powertransmission efficiency η thus obtained is transmitted to the powertransmission controller 30 b in every second cycle. When the powertransmission efficiency η falls to the threshold power efficiency ηth orless, the relay 47 is cut off.

In the wireless power supply system 102 according to the fourthembodiment, the power factor cos θ of the power output from the invertercircuit 12 is calculated by the power factor calculator 31, and thevoltage output from the AC/DC converter 11 is regulated when the powerfactor cos θ falls to the predetermined threshold power factor or less.The transmitted power can therefore be regulated for the first cycleshorter than the second cycle that is the communication cycle of thewireless communication unit 34, when the power factor cos θ isdecreased.

The power transmission efficiency η calculated by the efficiencycalculator 55 is transmitted to the power transmission controller 30 bfor the second cycle, and the power command value Pbat* is correctedbased on the power transmission efficiency η. When the powertransmission efficiency η falls to the threshold power efficiency ηth orless, the voltage Vdc output from the AC/DC converter 11 is regulatedand therefore, the transmitted power is regulated.

Accordingly, unnecessary power transmission can immediately besuppressed, so that trouble with the system such as heat generation canbe prevented, when the positions of the power transmission coil 14 andthe power receiving coil 41 are shifted from each other for some reason,such as a collision of the vehicle with another, or contrived movementof the vehicle. Further, a reduction of the power transmissionefficiency is detected by use of both the power factor cos θ (secondefficiency) calculated for the first cycle and the power transmissionefficiency η (first efficiency) obtained for the second cycle, and thetransmitted power is regulated when one of the efficiencies isdecreased. As a result, a margin for monitoring the transmitted powercan be provided, so as to control the power transmission with higheraccuracy.

When the power transmission efficiency η calculated by the power factorcalculator 55 falls to the predetermined threshold efficiency ηth orless, the relay 47 is cut off, so that the circuit on the powerreceiving device 40 side including the power receiving coil 41 and thebattery 44 is open as viewed from the power transmission coil 14 side.As a result, the impedance of the entire circuit, including the powertransmission coil 14, the power receiving coil 41, and the battery 44increases, and the phase difference between the current I1 and thevoltage V1 output from the inverter circuit 12 increases. Accordingly,the transmitted power is regulated, since the power factor cos θdecreases. Namely, the transmitted power from the power transmissiondevice 10 b can be regulated when the wireless communication between thewireless communication unit 34 and the wireless communication unit 51 isinterrupted, and when a problem with the power transmission efficiency ηis detected by the power receiving device 40.

Modified Example of Fourth Embodiment

A modified example of the fourth embodiment is described below. FIG. 15is a block diagram showing a configuration of a wireless power supplysystem according to the modified example of the fourth embodiment. Thewireless power supply system 103 shown in FIG. 15 differs from thewireless power supply system shown in FIG. 12 in that the powertransmission controller 30 c of the power transmission device 10 cincludes an efficiency calculator 19.

The power receiving controller 50 transmits the voltage Vbat detected bythe voltmeter 46 and the current Ibat detected by the ammeter 45 fromthe wireless communication unit 51. The wireless communication unit 34of the power transmission controller 30 c receives the voltage Vbat andthe current Ibat, which are stored in the memory 35.

The efficiency calculator 19 calculates the power Pbat supplied to thebattery 44 according to the voltage Vbat detected by the voltmeter 46and stored in the memory 35 and the current Ibat detected by the ammeter45 and stored in the memory 35. The efficiency calculator 19 furthercalculates the power transmission efficiency η by dividing the powerPbat by the power command value Pbat*. The efficiency calculator 19transmits the calculated power transmission efficiency η to the chargepower controller 36 and the inverter controller 32. The charge powercontroller 36 obtains the corrected power command value Pbat*′ based onthe power transmission efficiency η calculated by the efficiencycalculator 19. The other elements are the same as those shown in FIG. 12and therefore denoted by the same reference numerals, and detaildescriptions thereof are not repeated below.

The operation of the modified example according to the fourth embodimentis described below with reference to the flowcharts shown in FIG. 16 andFIG. 17. In FIG. 16, the processing from step S151 to step S155 isexecuted in the calculation cycle in the first process after thecalculation starts, and the following processing from step S156 isexecuted in the calculation cycle in the second process and repeated inthe subsequent cycles. The processing from step S151 to step S157 is thesame as that from step S111 to step S117 shown in FIG. [[3]] 13 andtherefore, the processing from step S158 is described below.

In step S158, the communication monitor 33 determines whether thecommunication cycle between the wireless communication unit 34 and thewireless communication unit 51 of the power receiving controller 50 isthe second cycle. The process proceeds to step S159 when thecommunication cycle is the second cycle (YES in step S158), and theprocess proceeds to step S164 when the communication cycle is not thesecond cycle (NO in step S158).

In step S159, the wireless communication unit 34 communicates with thewireless communication unit 51 of the power receiving controller 50. Instep S160, the wireless communication unit 34 receives the voltage Vbatand the current Ibat supplied to the battery 44. In step S161, thememory 35 updates the voltage Vbat and the current Ibat with newlyreceived data. Since the communication by the wireless communicationunit 34 is carried out in every second cycle, the voltage Vbat and thecurrent Ibat are updated by the memory 35 every time the second cyclehas passed.

In step S162, the efficiency calculator 19 calculates the power Pbatsupplied to the battery 44 by multiplying the voltage Vbat and thecurrent Ibat together, and further calculates the power transmissionefficiency η by dividing the power Pbat by the power command valuePbat*.

In step S163, the control amount calculator 29 corrects the powercommand value Pbat* by use of the power transmission efficiency η. Thecontrol amount calculator 29 obtains the corrected power command valuePbat*′ according to the following formula (4).

Pbat*′=Pbat*/η  (4)

In step S164, the control amount calculator 29 corrects the powercommand value Pbat* by use of the power factor cos θ. The control amountcalculator 29 obtains the corrected power command value Pbat*′ accordingto the following formula (3).

Pbat*′=Pbat*/cos θ  (3)

The process then proceeds to step S165. The processing from step S165 tostep S169 is the same as that from step S19 to step S23 shown in FIG. 3,and detail descriptions thereof are not repeated below.

Next, a processing procedure implemented by the power receivingcontroller 50 is described below with reference to the flowchart shownin FIG. 17. The processing in step S171 and step S172 is executed in thecalculation cycle in the second process after the calculation starts,and the following processing from step S173 is executed in thecalculation cycle in the second process and repeated in the subsequentcycles.

The processing from step S171 to step S176 is the same as that from stepS131 to step S136 shown in FIG. 14, and the processing from step S178 tostep S181 is the same as that from step S138 to step S141 shown in FIG.14. The procedure shown in FIG. 17 differs from that shown in FIG. 14 inthe process in step S177.

In step S177, the wireless communication unit 51 transmits the voltageVbat and the current Ibat which are the information of the battery 44.The process then proceeds to step S178. The voltage Vbat and the currentIbat transmitted from the wireless communication unit 51 is received bythe wireless communication unit 34 in step S160 shown in FIG. 16, andthen stored in the memory 35 in step S161.

In the fourth embodiment described above, the power receiving controller50 calculates the power transmission efficiency η, and transmits thecalculated power transmission efficiency η to the power transmissioncontroller 30 b. In the modified example of the fourth embodiment, thevoltage Vbat and the current Ibat is transmitted to the powertransmission controller 30 c, and the power transmission controller 30 cthen calculates the power transmission efficiency η.

The wireless power supply system 103 according to the modified examplecan achieve the same effects as the wireless power supply systemaccording to the fourth embodiment descried above. In the modifiedexample, since the power transmission controller 30 c calculates thepower transmission efficiency η, the calculation load in the powerreceiving controller 50 can be reduced.

Although the wireless power supply system and the power transmissiondevice according to the present invention have been described above byway of the embodiments shown in the drawings, the present invention isnot limited to the descriptions thereof, and the respectiveconfigurations can be replaced with optional ones having similarfunctions.

REFERENCE SIGNS LIST

-   10, 10 a, 10 b, 10 c POWER TRANSMISSION DEVICE-   11 AC/DC CONVERTER-   12 INVERTER CIRCUIT-   13 RESONANCE CIRCUIT-   14 POWER TRANSMISSION COIL-   15 INVERTER-   18 SUBTRACTOR-   19 EFFICIENCY CALCULATOR-   21 AMMETER-   22 VOLTMETER-   23 AMMETER-   24 VOLTMETER-   25 AMMETER-   26 VOLTMETER-   29 CONTROL AMOUNT CALCULATOR-   30, 30 a, 30 b, 30 c POWER TRANSMISSION CONTROLLER-   31 POWER FACTOR CALCULATOR-   32 INVERTER CONTROLLER-   33 COMMUNICATION MONITOR-   34 WIRELESS COMMUNICATION UNIT-   35 MEMORY-   36 CHARGE POWER CONTROLLER-   37 PRIMARY-SIDE CURRENT CALCULATOR-   38 PRIMARY-SIDE CURRENT CONTROLLER-   39 PFC CONTROLLER-   40 POWER RECEIVING DEVICE-   41 POWER RECEIVING COIL-   42 RESONANCE CIRCUIT-   43 RECTIFYING SMOOTHING CIRCUIT-   44 BATTERY-   45 AMMETER-   46 VOLTMETER-   47 RELAY-   50 POWER RECEIVING CONTROLLER-   51 WIRELESS COMMUNICATION UNIT-   52 COMMUNICATION MONITOR-   53 CAN COMMUNICATION UNIT-   54 RELAY CONTROLLER-   55 EFFICIENCY CALCULATOR-   56 BATTERY CONTROLLER-   57 VEHICLE CONTROLLER-   58 BUS LINE-   71 OVERCURRENT DETECTOR-   91 AC POWER SOURCE-   100, 101, 102, 103 WIRELESS POWER SUPPLY SYSTEM-   200 VEHICLE

1. A wireless power supply system comprising a power transmission deviceprovided on a ground side and having a power transmission coil, and apower receiving device provided in a vehicle and having a powerreceiving coil, the power transmission coil transmitting electric powerto the power receiving coil via a wireless connection, so as to supplythe electric power to an electrical load installed in the powerreceiving device, the power transmission device including: an efficiencycalculator configured to calculate a power transmission efficiency basedon a transmission power command value and the electric power supplied tothe electrical load; and a switching controller configured to stopsupplying the electric power received by the power receiving coil to theelectrical load when the power transmission efficiency falls to apredetermined threshold efficiency or less, the power transmissiondevice including: a power factor calculator configured to calculate apower factor based on a phase difference between a voltage and a currentsupplied to the power transmission coil; and a power controllerconfigured to control electric power supplied to the power transmissioncoil according to a transmission power command value, and regulate theelectric power supplied to the power transmission coil when the powerfactor falls to a predetermined threshold power factor or less since theelectric power supplied to the electrical load is stopped.
 2. (canceled)3. The wireless power supply system according to claim 1, wherein: thepower transmission device includes a power transmission-sidecommunication unit that communicates with the power receiving device,and the power receiving device includes a power receiving-sidecommunication unit that communicates with the power transmission device;and the power receiving device transmits the power transmissionefficiency to the power transmission device, so as to regulate theelectric power supplied to the power transmission coil when the powertransmission efficiency falls to the threshold efficiency or less. 4.(canceled)
 5. (canceled)